These words are used interchangeably to apply to an inborn tendency, natural impulse, or inner perception."My instinct was not to trust that man" probably means the same thing as "My intuition told me not to trust that man." An instinct is something inborn and natural, not dependent upon any thinking process of any kind (an instinct to fear falling from a height); intuition does not depend upon reasoning either but does convey the idea of knowledge and awareness: "a woman's intuition"; "a speaker's intuition that his talk is too intellectual." An infant is born with instincts, some of which are preserved into adulthood; an infant is born without intuition but forms opinions and judgments as he experiences life. A baby is born with the instinct to survive. Later, that baby becomes aware (has an intuition) that survival requires effort.
Dictionary of problem words and expressions. Harry Shaw. 1975.